Indicating current limiter with particle-filled body



Nov. 23, 1954 IJF. MATTHYSSE EIAL 2,695,348

INDICATING CURRENT LIMITER WITH PARTICLE-FILLED BODY Filed April 15,1953 United States Patent Ofiiice 2,695,348 Patented Nov. 23, 1954INDICATING CURRENT LIMITER WITH PARTICLE-FILLED BODY Irving F.Matthysse, Norwalk, Conn., and Leonard Greer, Bogota, N. J., assignorsto Burndy Engineering Co., Inc., a corporation of New York ApplicationApril 15, 1953, Serial No. 349,070 4 Claims. (Cl. 200-121) Our inventionrel-ates to current limiters and more particularly to a currentinterrupting device having visible indication of its condition.

Objects of our invention are to provide a lightweight airtight, accuratelimiter for aircraft adapted to withstand increased generator capacitiesand voltages used in present day aircraft without danger of explosionoccurring during the interruption, and which will give a positive andeasily visible indication of its condition.

These and other objects we accomplsh and obtain our new results as willbe apparent from the device described in the following specification,particularly pointed out in the claims, and illustrated in theaccompanying drawings, in which- Fig. l is a plan view, partly insection, of an embodiment of our indicating current limiter;

Fig. 2 is a side elevation thereof;

Fig. 3 is a cross-sectional view taken in the plane 3-3 of Fig. 2;

Fig. 4 is an end view of our device.

Fig. 5 is a perspective view of the indicator.

Our device comprises a glass tubular enclosure mounted to a pair ofknobs 12 provided with finger shields 14, a pair of contact blades 16and 18, a fusible element 20, and are suppressing means 22.

The glass enclosure which may be made of Pyrex, is capable ofwithstanding differential temperature conditions and shock withoutbreakage. The knobs are made of insulating material, such as a phenolicresin having shield portions overhanging the blades, so as to preventcontact therewith during installation or removal. The knobs are recessedas at 24 and 26 forming sockets to receive the ends of the glass. Thefusible element is usually made of silver wire brazed to the copperblades which support the element substantially centrally of the glasstube.

tion of the limiter from being ascertained. In order to permit suchinspection, we provide an indicator link 28,

and the glass envelope. A cross-shaped link with centrally extendingportions 30 aids in positioning and supporting the link on the innersurface of the glass envelope.

The silver fusible element being more conductive will carry most of thecurrent. When interrupted centrally within the sand filling, the currentwill be bypassed to the Nichrome Wire which normally carries a smallfraction of the main load. When the Nichrome link on the inner surfaceis interrupted, it will be readily apparent to the observer.

All the joints are fully sealed with cement 32 to prevent leakage, whichpermits the limiters to be used by aircraft at various heights withuniform limiter ratings.

For a readily discernible inspection of the condition of the fuse, abrght color changing paint is used which will discolor noticeably whenthe fuse is blown. An example of such indicating paint is identifiableon the open market as Pyromark, a trade product of the TempilCorporation of New Jersey.

We have thus described our invention, but we desire it understood thatit is not confined to the particular forms or uses shown and described,merely illustrative, ried out in other ways without departing from thespirit of our invention, and, therefore, we claim broadly the right toemploy all equivalent instrumentalities coming within the scope of theappended claims, and by means of which objects of our invention areattained and new results accomplished, as it is obvious that theparticular embodiments herein shown and described are only some of themany that can be employed to attain these objects and accomplish theseresults.

We claim:

1. A current limiter having a fusible element, a transparent envelopebody therefor, and contacts extending therefrom, said envelopecontaining an inert substance enclosing the fusible element forabsorbing the molten fuse particles when the circuit is interrupted,said fusible element having a parallel circuit of high resistance metalcontained Within the envelope body and extending toward the innersurface of the envelope body and barrier means for preventing the inertsubstance from enter- References Cited in the file of this patent UNITEDSTATES PATENTS Number Name Date 737,280 Sachs Aug. 25, 1903 1,443,136 LaMar Jan. 23, 1923 1,868,464 La Mar July 19, 1932 2,490,950 Dryer Dec.13, 1949

